//https://leetcode.cn/problems/contains-duplicate-ii/

class Solution
{
	public :
	bool containsNearbyDuplicate(vector<int>& nums, int k)
	{
		unordered_map<int, int> hash;
		for (int i = 0; i < nums.size(); i++)
		{
			if (hash.count(nums[i]))
			{
				if (i - hash[nums[i]] <= k) return true;
			} hash[nums[i]] = i;
		} return false;
	}
};